John Bollinger and myself have put our heads together and produced an ISO 14977 EBNF specification of CIF2.0 syntax. We were working from the 10 August 2011 "CIF Changes" document agreed by this group and approved in Madrid, available in the archives of this list at http://www.iucr.org/__data/iucr/lists/ddlm-group/pdf00001.pdf, with the following change:

Please study the attached EBNF (plain text format) and advise of any errors, omissions or ambiguities. Note that EBNF is clearly not the best format for machine-generation of parsers, but it should be sufficiently precise and understandable to serve as a foundation document for CIF2.

For those, such as myself, who have not seen the ENBF '-' operator before, the meaning of "A-B" is: all character sequences satisfying A, except those that satisfy B.

My intention is to start producing documentation for CIF2 on the basis of this EBNF, so your earliest comments would be most appreciated.

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